<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>成绩</title>
    <script>
        var score = prompt("请输入该学生成绩："); 
        var grade = (score>=80);
        var student=score>=80?alert("该学生的成绩为：A"):alert("该学生的成绩为：B");
    </script>
</head>
<body>
    
</body>
</html>